Many walk behind working machines, such as lawnmowers and other similar small powered equipment, have a self-propel system that propels or drives the working machine at a selected ground speed. In such systems, a control system is typically carried on the handle to allow the operator to engage and disengage the self-propel system and to select a desired ground speed. For example, many such control systems use a pivotable ground speed control bail on the handle of the working machine. In such systems, the bail can be pivoted to engage the self-propel system, with the degree of movement of the ground speed control bail dictating the ground speed of the working machine.
In these conventional self-propel systems, however, it can be difficult to maintain the control system in a fixed position corresponding to a desired cruising speed. For example, many control systems lack a fixed position in which the operator can comfortably hold the control bail while operating the working machine at a self-propelled “cruising” speed. In addition, with slipping belt or variable speed type transmissions that are commonly used in many lawnmowers, for example, the driving torque can change depending on the ground conditions such as the slope or ground surface. In such changing conditions, the speed of the transmission may require varying the control in a substantially continual manner to achieve a consistent desired speed.
In view of these issues, it would be desirable for a ground speed control system to allow for comfortable operation of the working machine at a cruising speed while still enabling changes in the driving torque to account for changing ground conditions.